Early prenatal food supplementation ameliorates the negative association of maternal stress with birth size in a randomised trial.

Low birthweight increases the risk of infant mortality, morbidity and poor development. Maternal nutrition and stress influence birth size, but their combined effect is not known. We hypothesised that an early-invitation time to start a prenatal food supplementation programme could reduce the negative influence of prenatal maternal stress on birth size, and that effect would differ by infant sex. A cohort of 1041 pregnant women, who had delivered an infant, June 2003-March 2004, was sampled from among 3267 in the randomised controlled trial, Maternal Infant Nutritional Interventions Matlab, conducted in Matlab, Bangladesh. At 8 weeks gestation, women were randomly assigned an invitation to start food supplements (2.5 MJ d(-1) ; 6 days a week) either early (∼9 weeks gestation; early-invitation group) or at usual start time for the governmental programme (∼20 weeks gestation; usual-invitation group). Morning concentration of cortisol was measured from one saliva sample/woman at 28-32 weeks gestation to assess stress. Birth-size measurements for 90% of infants were collected within 4 days of birth. In a general linear model, there was an interaction between invitation time to start the food supplementation programme and cortisol with birthweight, length and head circumference of male infants, but not female infants. Among the usual-invitation group only, male infants whose mothers had higher prenatal cortisol weighed less than those whose mothers had lower prenatal cortisol. Prenatal food supplementation programmes that begin first trimester may support greater birth size of male infants despite high maternal stress where low birthweight is a public health concern.